A licensed radio resource is a resource (e.g., in frequency) to which a license holder has been granted exclusive rights, e.g., by a government agency such as the Federal Communications Commission, FCC, in the United States. With exclusive rights, the license holder may transmit on a licensed radio resource without interference or resource crowding. This may allow the license holder to maximize resource efficiency and signal quality. Licensed radio resources are limited in number, though, which in turn limits their ability to meet the ever increasing demand for larger throughput from applications and services. Moreover, licensed radio resources are difficult and expensive to acquire.
By contrast, an unlicensed radio resource is a resource (e.g., in frequency) to which no license holder has been granted exclusive rights. Such a resource may therefore be simultaneously used by multiple operators or technologies, without the difficulty and expense associated with a licensed radio resource. Because the resource is shared, though, regulatory requirements may not permit transmissions on the unlicensed radio resource without first ensuring that the transmissions will not unduly interfere with other transmissions on the unlicensed radio resource (e.g., those that are already ongoing). This may be accomplished by performing a so-called clear channel assessment (CCA) or listen-before-talk (LBT) procedure, whereby a transmission is performed if the unlicensed radio resource is declared as idle but is otherwise deferred. An unlicensed radio resource may be used exclusively (e.g., by a MultiFire system) or be used as a complement to a licensed radio resource (e.g., by a Long Term Evolution Unlicensed, LTE-U, or Licensed-Assisted Access, LAA, system).
Use of an unlicensed radio resource proves complicated in some contexts, though. One such context occurs where a scheduling node schedules a transmission on the unlicensed radio resource in advance, e.g., on a dynamic basis. In doing so, the scheduling node “grants” the resource for a certain device to transmit or receive a transmission. The scheduling node accordingly transmits a so-called grant to that device. Notably, however, actual performance of the scheduled transmission still depends on the unlicensed radio resource being free for transmission when the time comes for the transmission to occur. Successful transmission of the grant to the device may also depend on the unlicensed radio resource being free for transmission, if that grant is transmitted on the unlicensed radio resource as well. These aspects complicate scheduling in a way that makes it difficult to optimize resource efficiency, latency, overhead, and throughput.